Why can’t I stop bleeding without the pill?

About 2 years ago, I got nexplanon implanted. It made me bleed for months straight, and I had to get it surgically removed due to it getting inserted into my muscle. I then got an IUD (worst pain of my life) and continued to bleed. I was put on birth control pills to “thicken my uterine lining”, but after months of those pills, every time I try to stop taking them, I bleed for endless periods of time. Do I have to just take birth control forever? What is wrong with me?